1. Field of the Invention
The present invention relates generally to hologram scanners and scanning processes. More particularly, it relates to hologram scanners for and to processes for forming a scanning line by diffracting and deflecting incident light.
2. Description of the Related Art
A typical hologram scanner uses a light source to emit a laser beam, a deflector that diffracts and deflects the incident laser beam, and an optical device to alter the proceeding direction of a scanning line, so that the laser beam diffracted and deflected by the deflector will be scanned in an in-scan direction across a photoreceptor medium, and successive scan lines will proceed in a predetermined direction. The deflector typically has a driving source that provides a rotation force, and a deflection disk with a plurality of sectors each having a hologram pattern.
The optical arrangement of the light source relative to the deflection disk is determined in terms of two restriction conditions. First, in recognition of the modulation feature of the laser diode, the minor axis of a light spot must be aligned in the in-scan direction of the photoreceptor medium. Second, the cross-sectional shape of the beam can be reversed according to a predetermined relation between the light spot and numerical aperture of a lens component. The ellipticity of the light spot inversely proportional to the numerical aperture because the wavelength of the light emitted from the laser diode is constant.
The efficiency of diffraction is influenced by the polarization of the incident light. Thus, in a conventional hologram scanner, when a comparison is made of the efficiency of diffraction, the light of transverse electric (TE) polarization can obtain the same efficiency of diffraction with a pattern that has a relatively lesser depth than the light of transverse electric (TE) polarization. In order to obtain a desired efficiency of diffraction with the light of TE polarization in a conventional scanner structure, a pattern of a relatively greater depth is needed with respect to the input of the light of TE polarization to the deflection disk. When a hologram pattern is formed that has a relatively greater depth relative to a fixed track pitch however, the shape of the pattern may be deformed and the efficiency of diffraction may be lowered. Consequently, it is difficult to manufacture the holographic pattern.
It is therefore, an object of the present invention to provide an improved hologram scanning process and hologram scanner.
It is another object to provide a hologram scanning process and hologram scanner for forming a scanning line by diffracting and deflecting incident light.
It is still another object to provide a hologram scanning process and hologram scanner able to easily form a hologram pattern with respect to a deflection disk by specifying the polarization direction of a laser beam input to the deflection disk.
It is yet another object to provide a hologram scanning process and hologram scanner in which light of TE polarization is incident upon a deflection disk so that a desired efficiency of diffraction can be obtained with a pattern having a relatively shallow depth.
Accordingly, these and other objects may be attained with a hologram scanning process and hologram scanner driving source to provide a rotational force, a deflection disk installed at the rotation shaft of the driving source for forming a scanning line, the deflection disk having a plurality of sectors where a hologram pattern for diffracting and deflecting incident light is formed, a TE polarized light emitting device, arranged to face one side of the deflection disk, for emitting TE polarized light so that major axis of an elliptical spot formed at a predetermined position on the deflection disk by the incident light is perpendicular to the radius vector of the deflection disk passing through the spot having an elliptical cross-section and a TE polarization mode, and an optical path altering device for altering the proceeding path of incident light so that a scanning line formed by the rotation of the deflection disk proceeds to a photoreceptor medium.